A stamping apparatus is used to form or “stamp” a metal blank into a finished part that is used for, for example, a panel of a vehicle. To ensure that the metal blank is securely located between upper and lower dies of the stamping apparatus, a binder is engaged to the blank to secure the blank to the lower die before the upper die is actuated to stamp the blank and form the finished part. To ensure that an edge of the blank does not move during the stamping process or at least most moves in a controlled manner, even when engaged by the binder, the binder may include a bead formed thereon that corresponds to a depression or recess formed in the lower die. Tensile strains experienced by the blank at these locations, however, may cause the blank to break during the stamping process, which may render the finished part unusable.
In addition to single bead configurations, multiple bead configurations are known to more securely clamp the blank before stamping. These multiple bead configurations, however, increase the amount of scrap generated during the stamping process, which increases manufacturing costs. In addition, multiple bead configurations do not ensure that the blank does not warp or break when experiencing tensile strains.
For example, referring to FIG. 1, a blank 2 is illustrated that is stamped using a conventional stamping apparatus (not shown) having a plurality of elongated draw beads. As illustrated, the elongated draw beads form elongated depressions 4 in the blank 2 during the stamping process when the blank 2 is constrained by a binder (not shown) of the stamping apparatus. As also illustrated, warps or buckles 6 can develop at locations between the depressions 4, which are undesirable in the finished part. The buckles 6 develop between the depressions 4 due to the lack of blank material present between the depressions 4 that can elastically stretch during the stamping process.